OK, first problem I had, stupid me, Didn't see IXtreme 1.6 for 83850C specifically. I tried the old one and ignored the error message. Stupid Me.
OK wierd now, I fixed my problem of E66 and RRoD by using Iprep, to restore it so that JungleFlasher could at least detect it was a 7850 drive. Don't know how I did it, but it did. Then I reflashed it to 83850C by manually spoofing it and now I can get to the Xbox Dashboard, but my DVD drive can't read backups or originals at all. Any advice?
May start from step 1 all over again and see what I can do, but will have to wait til tonight to try.